I would not put products like Duralube, Slick50, and MotorUp in a lawn mower engine, much less a car or truck engine. There are only a handful of oil supplements and cleaners that I believe it. I like Auto-RX, Neutra, Lube Control, Schaeffer's #132, and the Valvoline oil supplements might be okay. All of this other stuff that uses PTFE, chlorinated parrafin, and oil supplements that are just heavy mineral oil with a very small amount of chemical additives are all just rip off junk.
And many of the people who make oil supplements have been fined by the FTC for false advertising. Go to the FTC web site and check it out for yourself.
There are oil supplements being sold in this country that are inferior to standard quality conventional motor oil, and cost more then the standard motor oil. Go figure. The oil companies gave up on that chlorinated stuff a long time ago, because it caused corrosion. Not to mention the fact that it can cause cancer. Why would anybody want to put PTFE in an engine when there are chemical friction reducers that work just as well for less money and less potential damage to the engine?
Stick to good quality motor oil and you are better off. Have a dirty engine? Use Auto-RX or cleaning motor oils like Delvac 1. Can't afford Auto-RX? Try Neutra.